Commercially available and literature reported conductive inks can be used to print conductive traces of a conductive metal (e.g. silver) on a substrate with resistivity over 3 times, and typically over 7 times, that of the bulk conductive metal. These resistivity values are too high for many applications, such as RFID antennas. Further, inks are generally based on silver or silver-copper composite nanoparticles, which are expensive to produce and result in printed traces that need post-annealing (thermal or photonic) at a high temperature to sinter the particles. Only limited substrate materials resistant to the annealing temperature, normally 140° C., can be used for printing the inks. Thus, current conductive inks have high resistivity, are expensive, need a high temperature post-annealing process, and can be only printed on high-temperature resistant substrates, such as polyethylene terephthalates (PET), polyimides (PI) and polycarbonates (PC).
There is a need for a process for printing conductive inks that is one or more of lower resistivity, less cost, simpler processing and the ability to print on a wider range of substrates.